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United States Patent |
5,098,105
|
Sullivan
|
*
March 24, 1992
|
Golf ball compositions
Abstract
The present invention relates to improved cover compositions for golf ball
construction. The cover compositions comprise a blend of maleic anhydride
modified thermoplastic rubber elastomers, and ionomer resins.
In addition, the present invention is directed to golf balls produced
utilizing the improved cover compositions. The golf balls exhibit
properties of enhanced playability without sacrificing distance and/or
durability.
Inventors:
|
Sullivan; Michael J. (Chicopee, MA)
|
Assignee:
|
Lisco, Inc. (Tampa, FL)
|
[*] Notice: |
The portion of the term of this patent subsequent to January 22, 2008
has been disclaimed. |
Appl. No.:
|
642469 |
Filed:
|
January 17, 1991 |
Current U.S. Class: |
473/372; 260/998.14; 273/DIG.22; 473/385; 525/74; 525/941 |
Intern'l Class: |
A63B 037/12 |
Field of Search: |
273/235 R,234
524/908
260/998.14
|
References Cited
U.S. Patent Documents
4323247 | Jan., 1982 | Keches et al. | 260/998.
|
4483537 | Nov., 1984 | Hanada et al. | 524/908.
|
4526375 | Jul., 1985 | Nakade | 273/235.
|
4567219 | Jan., 1986 | Tominaga et al. | 524/908.
|
Other References
Abstract of Japanese Pat. No. 01-69656, Oki et al., 3/89.
|
Primary Examiner: Seccuro; Carman J.
Parent Case Text
This is a continuation-in-part of co-pending application, Ser. No.
07/449,774 filed on Dec. 13, 1989, now U.S. Pat. No. 4,986,545.
Claims
Having thus described the preferred embodiments, the invention is now
claimed to be:
1. A golf ball comprising a core and a cover, wherein the cover is formed
from a composition comprising about 5 to about 50 parts of a maleic
anhydride modified thermoplastic elastomer and about 95 to about 50 of an
ionomeric resin based on 100 parts by weight in the composition, wherein
said maleic anhydride modified thermoplastic elastomer consists of an
elastomer selected from the group consisting of a maleic anhydride
modified ethylene-propylene copolymer, a maleic anhydride modified
styrenic block copolymer polymer and a maleic anhydride modified
ethylene-vinyl acetate copolymer, and where said ionomeric resin is an
ionic copolymer of an olefin and a metal salt of an unsaturated carboxylic
acid.
2. A golf ball comprising a core and a cover, wherein the cover is formed
from a composition comprising about 15 to about 40 parts of a maleic
anhydride modified thermoplastic elastomer and about 85 to about 60 of an
ionomeric resin based on 100 parts by weight in the composition, wherein
said maleic anhydride modified thermoplastic elastomer consists of an
elastomer selected from the group consisting of a maleic anhydride
modified ethylene-propylene copolymer, a maleic anhydride modified
styrenic block copolymer polymer and a maleic anhydride modified
ethylene-vinyl acetate copolymer, and where said ionomeric resin is an
ionic copolymer of an olefin and a metal salt of an unsaturated carboxylic
acid.
3. A golf ball comprising a core and a cover, wherein the cover is formed
from a composition comprising about 20 to about 35 parts of a maleic
anhydride modified thermoplastic elastomer and about 80 to about 65 of an
ionomeric resin based on 100 parts by weight in the composition, wherein
said maleic anhydride modified thermoplastic elastomer consists of an
elastomer selected from the group consisting of a maleic anhydride
modified ethylene-propylene copolymer, a maleic anhydride modified
styrenic block copolymer polymer and a maleic anhydride modified
ethylene-vinyl acetate copolymer, and where said ionomeric resin is an
ionic copolymer of an olefin and a metal salt of an unsaturated carboxylic
acid.
Description
FIELD OF THE INVENTION
The present invention is directed to improved golf ball cover compositions
suitable for golf ball construction. More particularly, the present
invention relates to novel golf ball compositions comprised of a blend of
ionomeric resins and maleic anhydride modified thermoplastic elastomers.
In addition, the present invention is directed to golf balls produced
utilizing the improved cover compositions. The golf balls exhibit
properties of enhanced playability without sacrificing distance and/or
durability.
BACKGROUND OF THE INVENTION
Ionomeric resins are polymers containing interchain ionic bonding. As a
result of their toughness, durability, and flight characteristics, various
ionomeric resins sold either by E. I. DuPont deNemours & Company under the
trademark "Surlyn.RTM.", or by Exxon Corporation under the trademarks
"Escor.RTM." or "Iotek.RTM.", have become the materials of choice for the
construction of golf ball covers over the traditional "balata" (trans
polyisoprene, natural or synthetic) rubbers. The softer balata covers,
although exhibiting enhanced playability properties, lack the durability
necessary for repetitive play.
Ionomeric resins are generally ionic copolymers of an olefin such as
ethylene and a metal salt of an unsaturated carboxylic acid, such as
acrylic acid, methacrylic acid, or maleic acid. Metal ions, such as sodium
or zinc, are used to neutralize some portion of the acidic groups in the
copolymer resulting in a thermoplastic elastomer exhibiting enhanced
properties, i.e. durability, etc. for golf ball cover construction over
balata. However, the advantages gained in increased durability have been
offset to some degree by the decreases produced in playability.
While there are currently more than fifty commercial grades of ionomers
available from DuPont and Exxon with a wide range of properties which vary
according to the type and amount of metal cations, molecular weight,
composition of the base resin (i.e. relative content of ethylene and
methacrylic acid groups) and additive ingredients such as reinforcements
or additives, a great deal of research continues in order to develop golf
ball cover compositions exhibiting not only the enhanced impact resistance
and carrying distance properties produced by the "hard" ionomeric resins,
but also the playability (i.e. "spin") characteristics previously
associated with the "soft" balata covers, properties which are still
desired by the more skilled golfer. Thus, an object of the present
invention is to provide golf ball cover compositions which, when utilized
in golf ball construction, produce golf balls exhibiting improved
playability properties while maintaining satisfactory resilience and
durability.
As is indicated in U.S. Pat. No. 4,674,751, the patent literature is
replete with proposed cover formulations seeking to improve upon the
balata and ionomer covers which have been commercially successful, i.e.
see U.S. Pat. Nos. 3,819,768; 3,359,231; 4,398,000; 4,234,184; 4,295,652;
4,248,432; 3,989,568; 3,310,102; 4,337,947; 4,123,061, and 3,490,246.
However, none of these patents disclose and/or suggest the particular
compositions of the present invention and the improved characteristics
produced by golf balls formulated with such compositions.
The present invention is directed to new golf ball cover compositions which
exhibit properties of enhanced playability (i.e. softness and spin)
without sacrificing carrying distance (i.e. coefficient of restitution)
and/or durability. It has been found that these properties can be produced
by using ionomeric resins in combination with thermoplastic elastomers
modified with maleic anhydride. Along this line, the present inventor
discovered that contrary to the previous research in this area, the
addition of maleic anhydride modified thermoplastic elastomers to
ionomeric resin compositions greatly improves the playability properties
(i.e. decreases the hardness and increases the spin) of the compositions
without adversely affecting the desired properties (i.e. cut resistance
and/or resilience) produced by ionomeric resins.
SUMMARY OF THE INVENTION
The present invention is directed to improved golf ball cover compositions
and the resulting golf balls produced utilizing the cover compositions.
The novel golf ball cover compositions of the invention comprise a blend
of (1) thermoplastic elastomers modified with maleic anhydride, and (2)
ionomeric resins. When the cover compositions of the invention are
utilized to manufacture golf balls, the golf balls produced exhibit
properties of improved playability without sacrificing distance and/or
durability.
Two of the principal properties involved in the performance of golf balls
are resilience and hardness. Resilience is determined by the coefficient
of restitution (C.O.R.), the constant "e", which is the ratio of the
relative velocity of two elastic spheres after direct impact to that
before impact. As a result, the coefficient of restitution (i.e. "e") can
vary from zero to one, with one being equivalent to an elastic collision
and zero being equivalent to an inelastic collision.
Resilience (C.O.R.), along with additional factors such as clubhead speed,
angle of trajectory, and ball configuration (i.e. dimple pattern),
generally determines the distance a ball will travel when hit. Since
clubhead speed and the angle of trajectory are not factors easily
controllable, particularly by golf ball manufacturers, the factors of
concern among manufacturers are the coefficient of restitution (C.O.R.)
and the surface configuration of the ball.
The coefficient of restitution (C.O.R.) in solid core balls is a function
of the composition of the molded core and of the cover. In balls
containing a wound core (i.e. balls comprising a liquid or solid center,
elastic windings, and a cover), the coefficient of restitution is a
function of not only the composition of the center and cover, but also the
composition and tension of the elastomeric windings. Although both the
core and the cover contribute to the coefficient of restitution, the
present invention is directed solely to the coefficient of restitution
which is affected by the cover composition.
In this regard, the coefficient of restitution of a golf ball is generally
measured by propelling a ball at a given speed against a hard surface and
measuring the ball's incoming and outgoing velocity electronically. As
mentioned above, the coefficient of restitution is the ratio of the
outgoing velocity to incoming velocity. The coefficient of restitution
must be carefully controlled in all commercial golf balls in order for the
ball to be within the specifications regulated by the United States Golf
Association (U.S.G.A.). Along this line, the U.S.G.A. standards indicate
that a "regulation" ball cannot have an initial velocity (i.e. the speed
off the club) exceeding 255 feet per second. Since the coefficient of
restitution of a ball is related to the ball's initial velocity, it is
highly desirable to produce a ball having a sufficiently high coefficient
of restitution to closely approach the U.S.G.A. limit on initial velocity,
while having an ample degree of softness (i.e. hardness) to produce
enhanced playability (i.e. spin, etc.).
The hardness of the ball is the second principal property involved in the
performance of a golf ball. The hardness of the ball can affect the
playability of the ball on striking and the sound or "click" produced.
Hardness is determined as the deformation (i.e. compression) of the ball
under various load conditions applied across the ball's diameter (i.e. the
lower the compression value, the harder the material). As indicated in
U.S. Pat. No. 4,674,751, "softer" covers permit the accomplished golfer to
impart proper spin. This is because the softer covers deform on impact
significantly more than balls having "harder" ionomeric resin covers. As a
result, this allows the better player to impart fade, draw, or backspin to
the ball thereby enhancing playability. Such properties can be determined
by various "spin rate tests", such as the "nine-iron" spin rate test set
forth below.
Accordingly, the present invention is directed to new cover compositions
which produce, upon molding around solid or wound cores, golf balls
exhibiting a sufficient amount of hardness (i.e. softness) to improve the
playability of the balls without adversely affecting the ball's distance
(i.e. resilience) and/or durability (i.e. impact resistance, etc.).
These and other objects and features of the invention will be apparent from
the following description and from the claims.
DESCRIPTION OF THE INVENTION
The present invention relates to improved cover compositions for golf ball
construction. The cover compositions comprise a blend of maleic anhydride
modified thermoplastic elastomers and ionomer resins.
The thermoplastic elastomers suitable for use in the present invention
include maleic anhydride modified copolymers of ethylene and propylene
(i.e. ethylene-propylene rubbers (EPR)), styrenic block copolymers, and
ethylene-vinyl acetate copolymers (EVA). Styrenic block copolymers are
manufactured in the U.S. by The Shell Chemical Co. and marketed under the
tradenames of "Kraton D Rubber" (i.e. styrene-butadiene-styrene (SBS) and
styrene-isoprene-styrene (SIS types)), and "Kraton G Rubber" (i.e.
styrene-ethylene-butylene-styrene (SEBS) and
styrene-ethylene-propylene-styrene (SEPS)).
In this regard, it has been discovered that thermoplastic elastomers which
have been modified with maleic anhydride, such as a newly developed maleic
anhydride modified thermoplastic rubber sold by the Shell Chemical Co.
under the designation "Kraton FG 1901X", and a maleic anhydride modified
ethylene-vinyl acetate (EVA) copolymer sold by DuPont Canada Inc. under
the trademark "Fusabond.RTM.", are particularly well suited for use in
golf ball cover construction. When the Kraton FG 1901X maleic anhydride
modified thermoplastic rubber and the Fusabond.RTM. maleic anhydride
modified EVA (such as Fusabond.RTM. D-197) are blended with the specific
ionomeric resins at the proportions set forth below and applied to a solid
core to produce a molded golf ball, noticeable improvements in playability
(i.e. spin properties, etc.) of the ball are produced without sacrificing
the ball's durability (i.e. impact resistance, etc.), and/or resilience
(coefficient of restitution) which relates directly to the distance that a
golf ball will travel when struck under controlled conditions.
This is a particularly interesting discovery in that when the present
inventor had previously attempted to blend the softer unmodified
thermoplastic elastomers with the harder ionomeric resins in order to
improve the playability of the balls, the blends of the unmodified
thermoplastic elastomers-ionomeric resins suffered from inadequate
compatibility, and thus produced covers which exhibited very poor
durability (i.e. inadequate impact resistance). It was only when the
thermoplastic elastomers had been modified with a polar group, such as
maleic anhydride, and blended with the relatively hard ionomeric resins,
were improvements in both playability and durability exhibited. This is
because it is believed that the polar or maleic anhydride group interacts
(i.e. forms hydrogen bonds, etc.) with the acid groups of the ionomeric
resins to produce a more compatible and homogenous mixture than the
unmodified thermoplastic elastomers.
The maleic anhydride functionalized styrene block copolymers recently
developed by the Shell Chemical Co. have been found to be particularly
well suited for use in the present invention. Although these new
copolymers have been used to generate super-tough blends with nylons,
polyethylene terephthalate (PET), and PBT, and are also useful for
compatible blends of dissimilar polymers, it was unknown until the
development of the present invention that the modified styrenic block
copolymers could be blended with ionomer resins in order to produce
compositions useful for golf ball cover construction. As a result, Kraton
FG 1901X thermoplastic rubber, which is a maleic anhydride-functionalized
triblock copolymer consisting of polystyrene end blocks and
poly(ethylene/butylene) (i.e. styrene-ethylene-butylene-styrene block
copolymer (SEBS)) has been proven by the present inventor(s) to be an
effective additive for ionomeric resin cover blends.
Shown in Table 1 below is a comparison of the mechanical properties of
Kraton FG 1901X with "Kraton 1101", "Kraton G-2701", and "Kraton G-2706X",
three unmodified styrene-diene thermoplastic block copolymers sold by the
Shell Chemical Co.
TABLE 1
______________________________________
Typical Properties of Modified and Unmodified
Styrene-Diene Block Copolymers
Kraton
Kraton Kraton G-2701 Kraton
(SEBS) FG 1901X 1101 (SBS)
(SEBS) G-2706X
______________________________________
Specific 0.91 0.94 0.90 0.90
Gravity (g/cc)
Polymeric 28 30 NA NA
Styrene Content
(% weight)
Functionality
2 -- -- --
(% weight as
bound maleic
anhydride)
Hardness, 75 71 67 28
Shore A
Tensile 5,000 4,611 1,600 850
Strength, psi
Elongation at
500 880 260 950
Break. %
______________________________________
Furthermore, additional modified thermoplastic rubbers suitable for use in
the present invention include other maleic anhydride modified
thermoplastic rubbers currently under development by the Shell Chemical
Co. under the "Kraton" designation. Examples of these additional modified
thermoplastic rubbers include Kraton RP-6510 (containing about 0.5 weight
% maleic anhydride (MA)), Kraton RP-52-14 (containing about 2.5 weight %
maleic anhydride (MA)), Kraton RP-6505 (containing about 1.0% weight %
maleic anhydride (MA)) and others listed below in Table 2. In this regard,
Table 2 compares the variable differences of a large number of
developmental maleic anhydride functionalized block copolymers to that of
Kraton FG 1901X.
TABLE 2
______________________________________
Variable Differences in Developmental Maleic Anhydride
Functionalized Block Copolymers Relative
to Kraton FG 1901X
Developmental
3Block
Polymer Block Mole Wt.
Wt %
Polymer % MA Styrene Rubber Styrene
%
______________________________________
RP 52-14 2.5 NC NC NC NC
RP 6505 1.0 NC NC NC NC
RP 6510 0.5 NC NC NC NC
RP 50-1 NC + + NC NC
RP 50-3 + + + NC NC
RP 50-6 - + + NC NC
RP 6509 - - +VS - -
RP 6511-1 -- ++ ++ ++ --
RP 6511-2 - ++ ++ ++ --
RP 6511-3 - ++ ++ ++ --
______________________________________
NC = No Change
- = Decrease
+ = Increase
VS = Very Slight
These additional modified thermoplastic rubbers, when used in the
proportions and combinations set forth below to formulate golf ball cover
compositions, produce golf balls exhibiting enhanced coefficient of
restitution and durability without adversely affecting the playability of
the balls.
Moreover, as briefly mentioned above, it has been discovered that when
various maleic anhydride modified ethylene-vinyl acetate (EVA)
thermoplastic elastomers, such as those sold by Dupont under the trademark
"Fusabond.RTM.", are combined with the ionomer resins at the conditions
set forth below, a golf ball cover composition exhibiting the improved
results (i.e. enhance playability properties without a sacrifice in
distance and/or durability) desired in the present invention are also
produced. The properties, of the anhydride modified EVA compositions
currently sold by DuPont, i.e. vinyl acetate (VA) percentage, melt index
(MI) and weight percentage of maleic anhydride, are set forth below in
Table 3.
TABLE 3
______________________________________
FUSABOND .RTM. C [CHEMICALLY MODIFIED ETHYLENE-
VINYL ACETATE COPOLYMERS]
Grade % VA MI Wt % MALEIC ANHYDRIDE
______________________________________
D-189 33 20 1%
D-190 28 20 1%
D-197 18 2.5 1%
D-198 28 400 1%
D-199 33 200 1%
______________________________________
Furthermore, in addition to the above, it has been observed that the maleic
anhydride modified thermoplastic elastomers suitable for use in the
present invention may also be blended with unmodified thermoplastic
elastomers and ionomeric resins to produce golf balls exhibiting an
increase in the coefficient of restitution (i.e. rebound) while
maintaining the balls's overall playability characteristics. Along this
line, it is believed that the maleic anhydride modified thermoplastic
elastomers act as a compatibilizer between the unmodified thermoplastic
elastomers and the ionomeric resins. Since the unmodified thermoplastic
elastomers are less costly than the modified thermoplastic elastomers,
this observation offers many commercial advantages.
The ionomeric resins utilized to produce the cover compositions may be made
according to known procedures such as those in U.S. Pat. No. 3,421,766 or
British Patent No. 963,380, with neutralization effected according to
procedures disclosed in Canadian Patent Nos. 674,595 and 713,631, wherein
the ionomer is produced by copolymerizing the olefin and carboxylic acid
to produce a copolymer having the acid units randomly distributed along
the polymer chain. The ionic copolymer comprises one or more
.alpha.-olefins and from about 9 to about 20 weight percent of .alpha.,
.beta.-ethylenically unsaturated mono- or dicarboxylic acid, the basic
copolymer neutralized with metal ions to the extent desired.
At least 20% of the carboxylic acid groups of the copolymer are neutralized
by the metal ions, such as sodium, potassium, zinc, calcium, magnesium,
and the like, and exist in the ionic state.
Suitable olefins for use in preparing the ionomeric resins include, but are
not limited to, ethylene, propylene, butene-1, hexene-1, and the like.
Unsaturated carboxylic acids include, but are not limited to acrylic,
methacrylic, ethacrylic, .alpha.-chloroacrylic, crotonic, maleic, fumaric,
itaconic acids, and the like. Preferably, the ionomeric resin is a
copolymer of ethylene with acrylic and/or methacrylic acid. In addition,
two or more types of ionomeric resins may be blended into the cover
compositions in order to produce the desired properties of the resulting
golf balls.
Although the scope of the patent embraces all known ionomeric resins
suitable for use in the present invention, only a relatively limited
number of these ionomeric resins are commercially available. In this
regard, the ionomeric resins sold by E. I. DuPont de Nemours Company under
the trademark "Surlyn.RTM.", and the ionomer resins sold by Exxon
Corporation under the trademarks "Escor.RTM." or "Iotek.RTM." are examples
of commercially available ionomeric resins which may be utilized in the
present invention in the combinations described in detail below. The
ionomeric resins sold formerly under the designation "Escor.RTM." and now
under the new name "Iotek", are very similar to those sold under the
"Surlyn.RTM." trademark in that the "Iotek" ionomeric resins are available
as sodium or zinc salts of poly(ethylene acrylic acid) and the "Surlyn"
resins are available as zinc or sodium salts of poly(ethylene methacrylic
acid). In addition, various blends of "Iotek" and "Surlyn" ionomeric
resins, as well as other available ionomeric resins, may be utilized in
the present invention.
Examples of commercially available ionomeric resins which may be utilized
in the present invention include the sodium ionic copolymer sold under the
trademark "Surlyn 8940" and the zinc ionic copolymer sold under the
trademark "Surlyn 9910". Surlyn 8940 is a copolymer of ethylene with
methacrylic acid with about 15 weight percent acid which is about 29%
neutralized with sodium ions. This resin has an average melt flow index of
about 2.8. Surlyn 9910 is a copolymer of ethylene and methacrylic acid
with about 15 weight percent acid which is about 58% neutralized with zinc
ions. The average melt flow index of Surlyn 9910 is about 0.7. The typical
properties of Surlyn 9910 and 8940, as well as additional ionomeric resins
which may be utilized in the present invention, are set forth below in
Table 4.
TABLE 4
______________________________________
Typical Properties of Commerically Available
Surlyn Resins Suitable for Use in the Present Invention
ASTM D 9910 8940 AD-8265
AD-8269
______________________________________
Cation Sodium Zinc Sodium Sodium
Type
Melt flow
D-1238 2.8 0.7 0.9 0.9
index, gms/
10 min.
Specific
D-792 0.95 0.97 0.94 0.94
Gravity,
g/cm.sup.3
Hardness,
D-2240 --/66 --/64 92/39 84/25
Shore A/D
Tensile D-638 (4.8) 33.1
(3.6) 24.8
(4.2) 28.8
(3.1)21.2
Strength,
(kpsi), MPa
Elongation,
D-638 470 290 660 770
Flexural
D-790 (51)350 (48)330
(7.1)49.1
(2.8)19.3
Modulus,
(kpsi) MPa
Tensile D-18225 760(360) 1010(480)
494(235)
447(213)
Impact
(23.degree. C.)
KJ/m.sub.2 (ft.-
lbs./in.sup.2)
Melting DTA -- -- 81 72
Point, .degree.C.
Freezing
DTA -- -- 51 38
Point, .degree.C.
Vicat D-1525 63 62 51 48
Tempera-
ture, .degree.C.
______________________________________
In addition, examples of ionomer resins suitable for use in the present
invention sold under the "Iotek.RTM." trademark by the Exxon Corporation
include "Iotek 4000" (formerly "Escor 4000"), "Iotek 4010", "Iotek 8000"
(formerly Escor 900), "Iotek 8020", and "Iotek 8030". The typical
properties of the relatively "hard" Iotek ionomers are set forth below in
Table 5.
TABLE 5
__________________________________________________________________________
Typical Properties of Iotek Ionomers
ASTM
Method
Units
4000
4010
8000
8020
8030
__________________________________________________________________________
Resin
Properties
Cation type zinc
zinc
sodium
sodium
sodium
Melt index D-1238
g/10 min.
2.5
1.5
0.8
1.6
2.8
Density D-1505
kg/m.sup.3
963
963
954 960 960
Melting Point
D-3417
.degree.C.
90 90 90 87.5
87.5
Crystallization Point
D-3417
.degree.C.
62 64 56 53 55
Vicat Softening Point
D-1525
.degree.C.
62 63 61 64 67
Plaque
Properties
(3 mm thick,
compression molded)
Tensile at break
D-638
MPa 24 26 36 31.5
28
Yield point D-638
MPa none
none
21 21 23
Elongation at break
D-638
% 395
420
350 410 395
1% Secant modulus
D-638
MPa 160
160
300 350 390
Shore Hardness D
D-2240
-- 55 55 61 58 59
Film Properties
(50 micron film 2.2:1
Blow-up ratio)
Tensile at Break
MD D-882
MPa 41 39 42 52 47.4
TD D-882
MPa 37 38 38 38 40.5
Yield point
MD D-882
MPa 15 17 17 23 21.6
TD D-882
MPa 14 15 15 21 20.7
Elongation at Break
MD D-882
% 310
270
260 295 305
TD D-882
% 360
340
280 340 345
1% Secant modulus
MD D-882
MPa 210
215
390 380 380
TD D-882
MPa 200
225
380 350 345
Dart Drop impact
D-1709
g/micron
12.4
12.5
20.3
__________________________________________________________________________
Furthermore, in addition to the ionomeric resin indicated above, it has
also found that if a new acrylic acid based experimental soft ionomer
recently developed by the Exxon Corporation for the Spalding Sports
Worldwide, a division of Spalding & Evenflo Companies, Inc., Tampa, Fla.,
is utilized with the relatively hard ionomers described above, in the
combinations more clearly defined below and demonstrated in the Examples,
not only are improvements in processability and clarity seen, but also the
overall combinations, when utilized for golf ball construction, produced
golf balls having higher coefficient of restitution values (i.e. longer
distance) at equal or softer hardness than golf balls produced by known
hard-soft ionomer blends, including the hard-soft ionomer blends utilized
to produce Spalding's current Tour Edition.RTM. ball.
In this regard, the inventor has found that when the new ethylene-acrylic
acid based soft ionomer resins recently developed by the Exxon Corporation
under the designation "Iotek 7520" (referred experimentally by differences
in neutralization and melt indexes as LDX 195, LDX 196, LDX 218 and LDX
219) are combined with the relatively hard ionomers indicated above, the
combination produces higher C.O.R.s at equal or softer hardness, higher
melt flow (which corresponds to improved, more efficient molding, i.e.
fewer rejects), as well as significant cost savings versus balls produced
by known hard-soft ionomer blends due to lower overall raw materials costs
and improved yields.
While the exact chemical composition of the resins to be sold by Exxon
under the designation Iotek 7520 is considered by Exxon to be confidential
and proprietary information, Exxon's Experimental Product Data sheet lists
the following physical properties of the ethylene acrylic acid zinc
ionomer developed by Exxon:
TABLE 6
______________________________________
Property ASTM Method Units Typical Value
______________________________________
Physical Properties of Iotek 7520
Melt Index D-1238 g/10 min.
2
Density D-1505 kg/m.sup.3
0.962
Cation Zinc
Melting Point
D-3417 .degree.C.
66
Crystallization
D-3417 .degree.C.
49
Point
Vicat Softening
D-1525 .degree.C.
42
Point
Plaque Properties (2 mm thick Compression Molded Plaques)
Tensile at Break
D-638 MPa 10
Yield Point D-638 MPa None
Elongation at Break
D-638 % 760
1% Secant Modulus
D-638 MPa 22
Shore D Hardness
D-2240 32
Flexural Modulus
D-790 MPa 26
Zwick Rebond
ISO 4862 % 52
De Mattia Flex
D-430 Cycles >5000
Resistance
______________________________________
In addition, test data collected indicates that Iotek 7520 resins have
Shore D hardnesses of about 32-36 (per ASTM D-2240), melt flow indexes of
3.+-.0.5 g/10 min (at 190.degree. C. per ASTM D-1288), a flexural
moduluses of about 2500-3500 psi (per ASTM D-790). Furthermore, testing by
an independent testing laboratory by pyrolysis mass spectrometry indicates
that the Iotek 7520 resins are generally zinc salts of a terpolymer of
ethylene, acrylic acid, and methyl acrylate.
In view of the above information concerning the specific properties of the
critical components of the core composition, it has been discovered that a
golf ball can be generally produced in accordance with the present
invention from a central core and an outer cover wherein the outer cover
is made from a composition comprising a blend of about 5 to about 50 parts
by weight of a thermoplastic elastomer modified with maleic anhydride, and
about 95 to about 50 of an ionomeric resin based on 100 parts by weight
polymer in the composition.
More preferably, it has been found that a golf ball exhibited the
properties of enhanced playability and durability without sacrificing
traveling distance (i.e. C.O.R.) can be produced from a core and a cover
wherein the cover is made from a composition comprised of about 15 to
about 40 parts by weight of a thermoplastic elastomer modified with maleic
anhydride and about 85 to 60 parts by weight of an ionomeric resin based
on 100 parts by weight polymer in the composition.
Most preferably, the golf ball of the present invention can be produced
from a core and a cover wherein the cover is formed from a composition
comprising 20 to 35 parts by weight of a thermoplastic elastomer modified
with maleic anhydride and about 80 to about 65 parts of an ionomeric resin
based on 100 parts by weight polymer in the composition.
Additional materials may also be added to the compositions of the present
invention, dyes (for example, Ultramarine Blue sold by Whitaker, Clark,
and Daniels of South Plainsfield, N.J.), titanium dioxide, UV absorbers,
antioxidants, and stabilizers. Moreover, the cover compositions of the
present invention may also contain softening agents, such as plasticizers,
etc., and reinforcing materials such as glass fibers and inorganic
fillers, as long as the desired properties produced by the golf ball
covers of the invention are not impaired.
The cover compositions of the present invention may be produced according
to conventional melt blending procedures. Generally, the thermoplastic
elastomers modified with the polar groups, such as maleic anhydride, are
blended with the ionomeric resins in a Banbury type mixer, two-roll mill,
or extruder prior to molding. The blended composition is then formed into
slabs and maintained in such a state until molding is desired. If
necessary, further additives such as an inorganic filler, antioxidants,
stabilizers, and/or zinc oxide may be added and uniformly mixed before
initiation of the molding process.
Moreover, golf balls of the present invention can be produced by molding
processes currently well known in the golf ball art. Specifically, the
golf balls can be produced by injection molding or compression molding the
novel cover compositions about wound or solid molded cores to produce a
golf ball having a diameter of about 1.680 inches and weighing about 1.620
ounces. The standards for both the diameter and weight of the balls are
established by the United States Golf Association (U.S.G.A.). Although
both solid core and wound cores can be utilized in the present invention,
as a result their lower cost and superior performance, solid molded cores
are preferred over wound cores.
Conventional solid cores are typically compression molded from a slug of
uncured or lightly cured elastomer composition comprising a high cis
content polybutadiene and a metal salt of an .alpha., .beta.,
ethylenically unsaturated carboxylic acid such as zinc mono or diacrylate
or methacrylate. To achieve higher coefficients of restitution in the
core, the manufacturer may include a small amount of a metal oxide such as
zinc oxide. In addition, larger amounts of metal oxide than are needed to
achieve the desired coefficient may be included in order to increase the
core weight so that the finished ball more closely approaches the U.S.G.A.
upper weight limit of 1.620 ounces. Other materials may be used in the
core composition including compatible rubbers or ionomers, and low
molecular weight fatty acids such as stearic acid. Free radical initiator
catalysts such as peroxides are admixed with the core composition so that
on the application of heat and pressure, a complex curing or cross-linking
reaction takes place.
The term "solid cores" as used herein refers not only to one piece cores
but also to those cores having a separate solid layer beneath the cover
and above the core as in U.S. Pat. No. 4,431,193, and other multilayer
and/or non-wound cores.
Wound cores are generally produced by winding a very large elastic thread
around a solid or liquid filled balloon center. The elastic thread is
wound around the center to produce a finished core of about 1.4 to 1.6
inches in diameter, generally. Since the core material is not an integral
part of the present invention, a detailed discussion concerning the
specific types of core materials which may be utilized with the cover
compositions of the invention are not specifically set forth herein. In
this regard, the cover compositions of the invention may be used in
conjunction with any standard golf ball core.
As indicated, the golf balls of the present invention may be produced by
forming covers consisting of the compositions of the invention around
cores by conventional molding processes. For example, in compression
molding, the cover composition is formed via injection at about
380.degree. F. to about 450.degree. F. into smooth surfaced hemispherical
shells which are then positioned around the core in a dimpled golf ball
mold and subjected to compression molding at 200-300.degree. F. for 2-10
minutes, followed by cooling at 50-70.degree. F. for 2-10 minutes, to fuse
the shells together to form an unitary ball. In addition, the golf balls
may be produced by injection molding, wherein the cover composition is
injected directly around the core placed in the center of a golf ball mold
for a period of time at a mold temperature of from 50.degree. F. to about
100.degree. F. After molding the golf balls produced may undergo various
further processing steps such as buffing, painting, and marking.
The resulting golf balls produced from the novel ionomeric resin-polar
modified thermoplastic elastomers exhibit enhanced playability properties
over the art without sacrificing distance and/or durability. This is
because it is believed that the polar groups of the modified thermoplastic
interact with the acid and ionic groups of the ionomeric resins to produce
compatible mixtures which, upon processing, are sufficiently soft to
enhance playability but hard enough to maintain the coefficient of
restitution necessary for distance and durability.
The present invention is further illustrated by the following examples in
which the parts of the specific ingredients are by weight. It is to be
understood that the present invention is not limited to the examples, and
various changes and modifications may be made in the invention without
departing from the spirit and scope thereof.
EXAMPLES
By blending the ingredients set forth in the Tables below, a series of
cover formulations were produced. In the examples, cover formulations
containing thermoplastic elastomers modified with a polar group, such as
maleic anhydride, and a number of different types of ionomeric resins were
compared with unmodified thermoplastic elastomer-ionomer resins. In
addition, the properties produced by the cover compositions formulated
with the unmodified and modified thermoplastic elastomer-ionomeric resin
blends were compared to the properties produced by the cover materials
representative of the Tour Edition.RTM. (see Formulation 1) and the Top
Flite.RTM. (see Formulation 2) balls currently being sold by Spalding &
Evenflo Companies, Inc., Tampa, Fla. Although the specific formulations
utilized to produce the Tour Edition.RTM. and Top Flite.RTM. balls are
proprietary, these formulations were utilized under the same processing
conditions as those set forth below in order to produce covered golf balls
for comparison purposes.
Along this line, the Tour Edition.RTM. ball is unique in that it is a two
piece solid core, molded cover ball that meets the needs of golfers who
demand superior control, historically obtained only with balata covered
wound balls. It offers superior playability at the sacrifice of
coefficient of restitution, which relates directly to distance.
The Top Flite.RTM. ball is considered to be a "hard" Surlyn ionomeric resin
ball. As a result of the ball's hardness, the Top Flite.RTM. ball is a
difficult ball for golfers to control. Generally, the harder the golf
ball, the more difficult it is for a golfer to impart spin to the ball,
and hence, control the ball during flight. However, as a result of its
outstanding durability and maximum distance, the ball is widely accepted
by a large percentage of golfers.
The present invention is directed to a blend of (1) a thermoplastic
elastomers modified with a polar group, such as maleic anhydride, and (2)
an ionomeric resin, which, when utilized for golf ball cover compositions,
produces golf balls possessing the superior playability properties
exhibited by the current Top Flite.RTM. ball without sacrificing the
coefficient of restitution (i.e. distance) associated with the Tour
Edition.RTM. ball. In addition, the cover compositions of the present
invention exhibit enhanced durability over unmodified thermoplastic
elastomer-ionomeric resin compositions which possess some of the desired
properties of the cover compositions of the present invention.
The cover formulations set forth below in Tables 7 and 8 were injection
molded at 400.degree. F. around identical solid type cores having a
finished diameter of 1.545 inches to produce golf balls approximately
1.680 inches in diameter having nominal cover thickness of 0.0675 inches.
The properties of Riehle compression, coefficient of restitution (C.O.R.),
Shore Hardness, impact resistance, and spin rate for the cover formulation
were determined. In Tables 7 and 8, Formulations 5 and 10 are identical,
and Formulations 6 and 11 are similar (i.e. different unmodified
thermoplastic rubbers are utilized) in composition. These Examples have
been set forth for comparison purposes under two separate testing
conditions. The data for each example represents the average data for one
dozen balls produced according to the desired manner. The properties were
measured according to the following parameters:
Riehle compression is a measurement of the deformation of a golf ball in
inches under a fixed static load of 225 pounds
Coefficient of restitution (C.O.R.) was measured by firing the resulting
golf ball is an air cannon at a velocity of 125 feet per second against a
steel plate which is positioned 12 feet from the muzzle of the cannon. The
rebound velocity was then measured. The rebound velocity was divided by
the forward velocity to give the coefficient of restitution.
Shore hardness was measured in accordance with ASTM Test D-2240.
Cut resistance was measured in accordance with the following procedure: A
golf ball is fired at 135 feet per second against the leading edge of a
pitching wedge, wherein the leading edge radius is 1/32 inch, the loft
angle is 51 degrees, the sole radius is 2.5 inches, and the bounce angle
is 7 degrees
The cut resistance of the balls tested herein was evaluated on a scale of
1-5. 5 represents a cut that extends completely through the cover to the
core; a 4 represents a cut that does not extend completely through the
cover but that does break the surface; a 3 does not break the surface of
the cover but does leave a permanent dent; a 2 leaves only a slight crease
which is permanent but not as severe as 3; and a 1 represents virtually no
visible indentation or damage of any sort.
The spin rate of the golf ball was measured by striking the resulting golf
balls with a 9 iron in the manner as described above wherein the club-head
speed is about 80 feet per second and the ball is launched at an angle of
26 to 34 degrees with an initial velocity of about 110-115 feet per
second.
The spin rate was measured by observing the rotation of the ball in flight
using stop action Strobe photography.
Initial velocity is the velocity of a golf ball when struck at a hammer
speed of 143.8 feet per second in accordance with a test as prescribed by
the U.S.G.A.
TABLE 7
__________________________________________________________________________
Ingredients 1 2 3 4 5 6 7 8
__________________________________________________________________________
Kraton FG-1901X 15 -- 30 -- 22.5 --
Kraton G-2701
-- -- -- 15 -- 30 -- 22.5
Surlyn 9910 18.8 18.8 15.1 15.1 17.0 17.0
Surlyn 8940 -- -- 56.6 56.6 45.3 45.3 50.8 50.8
White MB 9.6 9.6 9.6 9.6 9.6 9.6
Properties
Melt Index
2160 g, 190 c
Weight, gms 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5
Riehle Compression
51 49 43 47 49 48 47 49
C.O.R. .802
.816
.811
.807
.805
.804
.809
.806
Shore A Hardness
90-91
98 94 95 91 91 92 92
Cut Resistance
2-3 2-3 2-3 2-3 3 5 2-3 3-4
(1 = Best, 5 = Worst)
Spin Properties
Launch Angle 27.6 28.4
Ball Speed
Spin Rate (RPM) 8626 8472
__________________________________________________________________________
TABLE 8
__________________________________________________________________________
Ingredients 1 2 9 10 11 12 13 14 15
__________________________________________________________________________
Kraton FG-1901X -- 30 -- -- 30 -- --
Kraton G-2706X -- -- 30 -- -- 30 --
Kraton RP-6510
-- -- -- -- -- 30 -- -- 30
Surlyn 9910 -- 15.1 15.1 15.1 -- -- --
Surlyn 8940 -- 45.3 45.3 45.3 -- -- --
Iotek 4000 45.2 -- -- -- 30.2 30.2 30.2
Iotek 8000 -- -- 45.2 -- -- -- 30.2 30.2 30.2
Surlyn White MB -- 9.6 9.6 9.6 -- -- --
Iotek White MB 9.6 -- -- -- 9.6 9.6 9.6
Melt Index 1.6 2.8 4.8 0.66
2.9 1.0 1.3 6.1 2.5
2160 g, 190 c
Weight, gms 45.7 45.6 45.7 45.3 45.5 45.3 45.4 45.3 45.4
Riehle Compression
54 51 48 52 55 54 54 54 53
C.O.R. .792
.804
.809
.797
.795
.800
.802
.800
.803
Shore C Hardness
87-88
95-96
96 87-88
86-87
87 89-90
88-89
88-89
Cut Resistance
2-3 2-3 2-3 2-3 4-5 2-3 2-3 4-5 2-3
(1 = Best, 5 = Worst)
Spin Properties
Launch Angle
30.0 31.8 32.6 29.7 29.8 30.2 30.4 30.7 30.4
Ball Speed 113.2
112.7
112.8
114.6
114.1
113.8
113.6
113.7
113.8
Spin Rate (RPM)
10117
8817 8066 10260
10218
10010
9706 9594 9679
__________________________________________________________________________
Discussion of the Examples
As indicated above, although blends of unmodified thermoplastic rubbers
with ionomeric resins generally produce softer covers which exhibit
enhanced playability, these covers have very poor durability. This is
evident in Formulations 6, 8, 11, and 14. In Formulations 6 and 8, Kraton
G-2701 is blended with hard Surlyn grades 9910 and 8940 to produce
relatively soft covers (i.e. Riehle Compressions of 48 and 49 and C.O.R.s
of 0.804 and 0.806) in comparison to the hard Top Flite.RTM. cover
composition set forth in Formulation 2 (i.e. the Top Flite.RTM. covers
exhibit an average compression of 45 and an average C.O.R. of 0.816). The
same can be seen in Formulations 11 and 14 except Kraton G-2706X was
utilized as the unmodified thermoplastic rubber. In addition, in
Formulations 14, Iotek 4000 and Iotek 8000 were substituted for the Surlyn
ionomeric resins.
In this regard, significantly higher compressions, lower hardness values,
and lower C.O.R.s indicate that the balls would have a softer feel and are
thus, more readily deformed by a golf club. As a result of the additional
deformation, a golfer can put more spin on the ball and, hence, impart
better control over the ball.
However, while softer covers were produced by the unmodified thermoplastic
rubber-ionomeric resin blends, the durability of the covers also
drastically decreased. This can be seen in the cut resistance values of
4-5. The results are very similar to those produced by balata covered
balls. Thus, while the playability of the covers produced from the
unmodified thermoplastic rubber-ionomeric resin blends increased to some
degree, the durability of the covers produced was insufficient for
repetitive play.
Formulations 5 and 7 in Table 7 and Formulations 10, 12, 13, and 15 in
Table 8 involve cover formulations produced according to the present
invention. Specifically, these formulations involve covers produced from
various polar modified (i.e. maleic anhydride modified) thermoplastic
rubber-ionomer resin blends. Formulation 12 is similar to Formulation 10
except Kraton RP-6510 is used as the modified thermoplastic rubber
elastomer as opposed to FG-1901-X. Formulations 13 and 15 are similar to
Formulations 10 and 12 respectively, except that the Surlyn ionomeric
resins were substituted With Iotek ionomeric resins. The pigment
concentrates were also changed to enhance compatibility.
The examples of the present invention (i.e. Formulations 5, 7, 10, 12, 13,
and 15) exhibit properties of enhanced playability demonstrated by the
unmodified thermoplastic rubber-ionomeric resins without sacrificing
distance and/or durability. This can be seen in that the Riehle
compressions, Shore C hardness, and C.O.R.s of the covers of the
formulations of the present invention are similar to the covers of the
unmodified thermoplastic rubber-ionomeric resin formulations. For example,
the values of the average Riehle compressions and C.O.R.s for Formulations
5 and 7 are 48 and 0.807, respectively, and for Formulations 6 and 8 the
values are 48.5 and 0.805 respectfully. These values are very close to the
intermediate values produced by the combination of the desired properties
of the Tour Edition.RTM. ball (Formulation 1) and the Top Flite.RTM. ball
(Formulation 2).
Furthermore, as demonstrated by the cut resistance results, the durability
of the cover compositions of the present invention (i.e. 2-3 in
Formulations 5 and 7) is greatly improved over the unmodified
thermoplastic rubber-ionomeric resin blends of Formulations 6 and 8 (i.e.
4-5). The same results can be seen in the comparison of Formulations 10,
12, 13 and 15 which are directed to the polar modified thermoplastic
rubber-ionomer resin blends of the present invention versus Formulations
11 and 14 concerning the unmodified thermoplastic rubber-ionomer resin
formulations.
In addition, in order to demonstrate that other maleic anhydride
functionalized thermoplastic rubber elastomers sold under the "Kraton"
trademark are also effective in the present invention, the above
Formulations were repeated with additional maleic anhydride modified
Kraton rubbers. In this regard, Kraton RP-6510 contains about 0.5 weight
percent maleic anhydride, Kraton RP-5214 contains about 2.5 weight percent
maleic anhydride, and RP-6505 1.0 weight percent maleic anhydride. The
results listed in Table 9 below demonstrate that the additional maleic
anhydride modified thermoplastic rubber elastomers when blended with
ionomeric resins such as those sold under the Surlyn.RTM. designation
offer higher coefficient of restitution (C.O.R.) than the current Tour
Edition.RTM. ball. See Formulations 17-20.
In addition, the data set forth in Table 9, indicates that blends of maleic
anhydride modified thermoplastic rubbers and unmodified thermoplastic
rubbers produce increases in the coefficient of restitution (C.O.R.) over
the current Tour Edition.RTM. ball. As mentioned above, it is believed
that the maleic anhydride modified thermoplastic elastomers act as a
compatibilizer between the unmodified thermoplastic elastomers and the
ionomer resins.
TABLE 9
__________________________________________________________________________
% MA
1 2 16 17 18 19 20 21
__________________________________________________________________________
Kraton FG-1901X
2.0 15.0 -- -- -- -- 15.0
Kraton 2706X
-- 15.0 -- -- -- -- --
Kraton 1651
-- -- -- -- -- -- -- -- 15.0
Kraton RP-6510
.5 -- 30.0 -- -- -- --
Kraton RP-52-14
2.5 -- -- 30.0 -- -- --
Kraton RP-6505
1.0 -- -- -- 30.0 -- --
Kraton RP-6501
-- -- -- -- -- -- -- 30.0 --
Surlyn 9910
-- 15.1 15.1 15.1 15.1 15.1 15.1
Surlyn 8940
-- 45.3 45.3 45.3 45.3 45.3 45.3
White Masterbatch
-- 9.6 9.6 9.6 9.6 9.6 9.6
Weight 45.6 45.4 45.6 45.3 45.4 45.4 45.3 45.7
Compression 57 52 55 54 54 56 55 54
C.O.R. .807
.820
.810
.813
811
.810
.811
.808
Shore C Hardness
83 87 82 84 85 83 85 84
Cut Resistance
2-3 2-3 2-3 2-3 2-3 2-3 2-3 2-3
(1 = No mark
5 = Clean cut)
__________________________________________________________________________
As a result, the golf ball cover compositions of the present invention
produces golf balls exhibiting properties of enhanced playability without
sacrificing distance and/or durability.
Moreover, the process set forth in the above examples was also repeated for
the maleic anhydride (MA) modified EVA/Ionomeric resin formulations set
forth in Tables 10 and 11 below in order to demonstrate the effectiveness
of these combinations for golf ball cover construction. Specifically in
Table 10, the properties (C.O.R. and compression) of various blends of
relatively hard ionomeric resins (i.e. Iotek 4000 and 8000) with maleic
anhydride modified EVA (i.e. Fusabond D-189 (33% V.A., 20 M.I., and 1%
maleic anhydride) or Fusabond D-197 (18% V A., 2.5 M.I., and 1% maleic
anhydride)) and/or unmodified EVA (i.e. Elvax.RTM. 460, (18% V.A., 2.5
M.I.) trademarked and sold by DuPont) were compared.
TABLE 10
__________________________________________________________________________
22 23 24 25 26 27 28 29
__________________________________________________________________________
Iotek 4000
50 42.5 42.5 35 35 35 42.5 35
Iotek 8000
50 42.5 42.5 35 35 35 42.5 35
Fusabond D-189
-- 15 -- 30 -- -- -- --
Fusabond D-197
-- -- 15 -- 30 10 -- --
ELVAX 460
-- -- -- -- -- 20 15 30
C.O.R. .814
.796
.809
.796
.802
.801
.803
.800
Compression
53 56 55 58 61 59 57 57
__________________________________________________________________________
The results indicate that the ionomeric resins/maleic anhydride (MA)
modified EVA blends (i.e. Formulations 24 and 26) provide higher C.O.R.
values than the ionomeric resins/unmodified EVA blends (i.e. Formulations
28 and 29). In this comparison, since ionomeric resin blend and the weight
percent of vinyl acetate (i.e. 18%) and the melt index (i.e. 2.5) of the
EVA compositions (i.e. Fusabond D-197 and Elvax 460) were exactly the
same, the only differences was the inclusion of maleic anhydride
modification to the EVA component of the composition. The data
demonstrates that the incorporation of maleic anhydride (MA) modified EVA
with the ionomeric resins produces a cover composition exhibiting enhanced
C.O.R. values with little or no change in hardness over the unmodified
EVA/ionomeric resin blends.
In Table 11 below, blends containing the incorporation of a maleic
anhydride modified EVA (i.e. Fusabond D-197 in Formulations 33 and 34)
with various ionomeric resins (specifically, relatively hard ionomeric
resins Iotek 4000 and 8000) were compared with blends comprising of i)
unmodified EVA/ionomeric resins (i.e. Formulation 38), ii) maleic
anhydride modified and unmodified EVA/ionomeric resins (i.e. Formulation
37), iii) maleic anhydride modified thermoplastic rubber
elastomer/ionomeric resins (i.e. Formulations 35 and 36), iv) relatively
hard ionomeric resins (i.e. Formulations 30), and v) relatively hard and
soft ionomeric resins.
TABLE 11
__________________________________________________________________________
30 31 32 33 34 35 36 37 38
__________________________________________________________________________
Iotek 4000
45.2 37.7 30.2 37.7 30.2 40.2 35.2 30.2 30.2
Iotek 8000
45.2 37.7 30.2 37.7 30.2 40.2 35.2 30.2 30.2
Iotek 7520
-- 15 30 -- -- -- -- -- --
Fusabond D-197
-- -- -- 15 30 -- -- 15 --
Iotek White
9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6
Kraton FG 1901X
-- -- -- -- -- 10 20 -- --
ELVAX 460 -- -- -- -- -- -- -- 15 30
Weight 45.4 45.4 45.5 45.4 45.0 45.5 45.3 45.3 45.4
Compression
50 53 54 53 55 52 54 54 54
C.O.R. .801
.794
.790
.794
.788
.796
.793
.789
.788
Share D. Hardness
67 64 60 64 62 65 63 59 60
Guillotine
VG VG G VG G VG G G CC
(VG = very good
G = good
F = fair
CC = Cut to Core)
__________________________________________________________________________
The data demonstrates that the inclusion of maleic anhydride modification
is necessary in order to produce an EVA/ionomeric resin blend having the
durability required for golf ball cover construction. In addition, the
data indicates that the improved properties produced by the inclusion of
the maleic anhydride modified thermoplastic rubber elastomers (i.e. Kraton
FG-1901X) to the ionomer resins are also produced by the inclusion of the
maleic anhydride modified EVA to the resins. Further, the data also shows
that the inclusion of the maleic anhydride modified EVA (i.e. Fusabond
D-197) with the relatively hard ionomeric resins (i.e. Iotek 4000 and
Iotek 8000) produces similar C.O.R. and hardness values as the inclusion
of the much more costly soft ionomeric resin Iotek 7520.
As a result, the relatively low cost maleic anhydride modified EVA (i.e.
Fusabond D-197 is approximately $1.30/lb.) can be used as a replacement
for the relatively expensive soft ionomer (Iotek 7520 is approximately
$2.00/lb.). Further cost savings can be achieved by using a blend of the
maleic anhydride modified EVA and the unmodified EVA (Elvax 460 is
approximately $0.70/lb) without much of a sacrifice in properties.
However, as indicated above, as a result of the durability difficulty, the
unmodified EVA can not be utilized alone with the ionomeric resins. Thus,
although it has been known that use of ionomeric resin blends with
unmodified EVA gives generally poor results, the improvements associated
with the replacement of the unmodified EVA with maleic anhydride modified
EVA are surprising and beneficial from both a performance and cost
standpoint.
The invention has been described with reference to the preferred
embodiments. Obviously, modifications and alterations will occur to others
upon reading and understanding the preceding detailed description. It is
intended that the invention be construed as including all such alterations
and modifications insofar as they come within the scope of the claims and
the equivalents thereof.
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